Currently 30-40 million dogs and cats are fed in Japan. 70% or more of them eat commercially available pet food. On the one hand commercially available pet food is widely used for a reason that it has an advantage that long term storage is possible and an advantage that nutrients necessary to a pet are contained in a balanced manner, or other reasons, but on the other hand problems are pointed out that a great amount of additives such as preservative, antiseptic, antioxidant or the like are contained so that there is a risk that pet's health is impaired, and that the nutrients contained are from chemical substances.
In view of such problems, guardians are increasing who do not use commercial pet food but prepare handmade food at home. However, preparing food for a pet everyday requires great care and is not easy. Especially, though a guardian sometimes entrusts a pet to a pet hotel or an acquaintance during a travel or a business trip, it is not easy, in such a case, to prepare food for a few days or to instruct the pet hotel or the acquaintance to give properly the prepared food to the pet. As a result of such problems, many guardians tend to use commercial pet food for convenience, though they believe that handmade food is preferable for maintaining pet's health.
Incidentally, a manufacturing method of additive-free pet food is disclosed in Patent Document 1. According to this document, it is possible to manufacture pet food that can be stored as long as one year or more by combining a plurality of heating processes and cooling processes. Although the pet food manufactured by such a method is much more preferable for pet's health than pet food containing additives, it is accompanied by problems that the cost is necessarily high owing to complicated processes, and that it is difficult to vary the nutrient components, texture, taste and the like of the pet food in accordance with the health condition, constitution, and preference of individual pets, because mass production of pet food of the same kind is assumed.
Further, a manufacturing method of pet food which allows manufacturing pet food in accordance with the guardian's request is disclosed in Patent Document 2. According to the method disclosed in this document, since pet food is manufactured of materials in accordance with the guardian's request, it is possible to satisfy the health condition, constitution, or preference of individual pets to a certain degree. However, the method is implemented by a large scale apparatus disposed in a pet-related shop, so that it is necessary to go to the pet-related shop every time the pet food is required, and since no additives are included, a long-term storage is limited so that it is not practical to buy a large amount at once, which makes it necessary to go frequently to the pet-related shop and is troublesome.